The number of circles that touch all the three lines x + y – 1 = 0, x – y – 1= 0 and y + 1 = 0 is 
 

Plotting the given lines, we observe that they form a right angled triangle.

Every triangle have 1 incircle and 3 excircles.

∴ Number of circles that can be drawn touching all the three lines x+y−1=0, x−y−1=0 and y+1=0 is 4